| Oenothera hybr. | | a | |
| Oenothera spp. | | a | |
| Oenothera acuticarpa W. Dietr. | Oenothera siambonensis W. Dietr. | | |
| Oenothera acutifolia Rostanski, nom. inval. | Oenothera biennis L. | | |
| Oenothera affinis Cambess. | | a | |
| Oenothera albicaulis Pursh | | a | |
| Oenothera albicaulis Pursh var. runcinata Engelm. | Oenothera pallida Lindl. subsp. runcinata (Engelm.) Munz & W. M. Klein | | i |
| Oenothera ammophila Focke | Oenothera oakesiana (A. Gray) J. W. Robbins ex S. Watson | | |
| Oenothera amoena Lehm. | Clarkia amoena (Lehm.) A. Nelson & J. F. Macbr. subsp. amoena | | |
| Oenothera andina Nutt. | Holmgrenia andina (Nutt.) W. L. Wagner & Hoch | | |
| Oenothera arborea Kellogg | Xylonagra arborea (Kellogg) Donn. Sm. & Rose | | |
| Oenothera arcuata Kellogg | Clarkia arcuata (Kellogg) A. Nelson & J. F. Macbr. | | |
| Oenothera arequipensis Munz & I. M. Johnst. | | a | |
| Oenothera argillicola Mack. | | a | |
| Oenothera atrovirens Shull & Bartlett | Oenothera parviflora L. | | |
| Oenothera austromontana (Munz) P. H. Raven et al. | Oenothera nutans G. F. Atk. & Bartlett | | |
| Oenothera avita (W. E. Klein) W. E. Klein subsp. eurekensis (Munz & John C. Roos) W. M. Klein | Oenothera californica (S. Watson) S. Watson subsp. eurekensis (Munz & John C. Roos) W. M. Klein | | i |
| Oenothera bahia-blancae W. Dietr. | | a | |
| Oenothera berlandieri (Spach) Steud. | | a | |
| Oenothera berteroana Spach | Oenothera affinis Cambess. | | |
| Oenothera biennis L. | | a | |
| Oenothera biennis L. subsp. austromontana Munz | Oenothera nutans G. F. Atk. & Bartlett | | i |
| Oenothera biennis L. var. hirsutissima A. Gray ex S. Watson | Oenothera elata Kunth subsp. hirsutissima (A. Gray ex S. Watson) W. Dietr. | | i |
| Oenothera biennis L. var. sulfurea Kleb., nom. nud. | Oenothera biennis L. | | i |
| Oenothera bifrons D. Don | Oenothera heterophylla Spach | | |
| Oenothera biloba Durand | Clarkia biloba (Durand) A. Nelson & J. F. Macbr. | | |
| Oenothera bistorta Nutt. ex Torr. & A. Gray | Camissonia bistorta (Nutt. ex Torr. & A. Gray) P. H. Raven | | |
| Oenothera blandina de Vries | Oenothera glazioviana Micheli | | |
| Oenothera boothii Douglas | Eremothera boothii (Douglas) W. L. Wagner & Hoch | | |
| Oenothera brachycarpa A. Gray | | a | |
| Oenothera brevipes A. Gray | Chylismia brevipes (A. Gray) Small subsp. brevipes | | |
| Oenothera brevipes A. Gray subsp. arizonica P. H. Raven | Chylismia brevipes (A. Gray) Small subsp. arizonica (P. H. Raven) W. L. Wagner & Hoch | | i |
| Oenothera brevipes A. Gray var. pallidula Munz | Chylismia brevipes (A. Gray) Small subsp. pallidula (Munz) W. L. Wagner & Hoch | | i |
| Oenothera californica (S. Watson) S. Watson | | a | |
| Oenothera californica (S. Watson) S. Watson subsp. californica | | a | i |
| Oenothera californica (S. Watson) S. Watson subsp. eurekensis (Munz & John C. Roos) W. M. Klein | | a | i |
| Oenothera campylocalyx K. Koch & C. D. Bouche | Oenothera versicolor Lehm. | | |
| Oenothera canescens Torr. & Frem. | | a | |
| Oenothera canovirens E. Steele | Oenothera villosa Thunb. subsp. villosa | | |
| Oenothera catharinensis Cambess. | | a | |
| Oenothera cavernae Munz | | a | |
| Oenothera cespitosa Nutt. | | a | |
| Oenothera cespitosa Nutt. subsp. cespitosa | | a | i |
| Oenothera cespitosa Nutt. subsp. marginata (Nutt. ex Hook. & Arn.) Munz | | a | i |
| Oenothera cheiranthifolia Hornem. ex Spreng. | Camissoniopsis cheiranthifolia (Hornem. ex Spreng.) W. L. Wagner & Hoch subsp. cheiranthifolia | | |
| Oenothera cheiranthifolia Hornem. ex Spreng. var. suffruticosa S. Watson | Camissoniopsis cheiranthifolia (Hornem. ex Spreng.) W. L. Wagner & Hoch subsp. suffruticosa (S. Watson) W. L. Wagner & Hoch | | i |
| Oenothera cheradophila Bartlett | Oenothera villosa Thunb. subsp. strigosa (Rydb.) W. Dietr. & P. H. Raven | | |
| Oenothera chicagoensis Renner ex R. E. Cleland & Blakeslee, nom. nud. | Oenothera biennis L. | | |
| Oenothera cinerea (Wooton & Standl.) W. L. Wagner & Hoch | | a | |
| Oenothera claviformis Torr. & Frem. | Chylismia claviformis (Torr. & Frem.) A. Heller subsp. claviformis | | |
| Oenothera claviformis Torr. & Frem. subsp. funerea P. H. Raven | Chylismia claviformis (Torr. & Frem.) A. Heller subsp. funerea (P. H. Raven) W. L. Wagner & Hoch | | i |
| Oenothera claviformis Torr. & Frem. subsp. integrior P. H. Raven | Chylismia claviformis (Torr. & Frem.) A. Heller subsp. integrior (P. H. Raven) W. L. Wagner & Hoch | | i |
| Oenothera claviformis Torr. & Frem. subsp. rubescens P. H. Raven | Chylismia claviformis (Torr. & Frem.) A. Heller subsp. rubescens (P. H. Raven) W. L. Wagner & Hoch | | i |
| Oenothera claviformis Torr. & Frem. subsp. wigginsii P. H. Raven | Chylismia claviformis (Torr. & Frem.) A. Heller subsp. wigginsii (P. H. Raven) W. L. Wagner & Hoch | | i |
| Oenothera claviformis Torr. & Frem. subsp. yumae P. H. Raven | Chylismia claviformis (Torr. & Frem.) A. Heller subsp. yumae (P. H. Raven) W. L. Wagner & Hoch | | i |
| Oenothera claviformis Torr. & Frem. var. peeblesii Munz | Chylismia claviformis (Torr. & Frem.) A. Heller subsp. peeblesii (Munz) W. L. Wagner & Hoch | | i |
| Oenothera claviformis Torr. & Frem. var. peirsonii Munz | Chylismia claviformis (Torr. & Frem.) A. Heller subsp. peirsonii (Munz) W. L. Wagner & Hoch | | i |
| Oenothera clelandii W. Dietr. et al. | | a | |
| Oenothera coloradensis (Rydb.) W. L. Wagner & Hoch | | a | |
| Oenothera coloradensis (Rydb.) W. L. Wagner & Hoch subsp. coloradensis | | a | i |
| Oenothera coloradensis (Rydb.) W. L. Wagner & Hoch subsp. neomexicana (Wooton) W. L. Wagner & Hoch | | a | i |
| Oenothera contorta Douglas | Camissonia contorta (Douglas) Kearney | | |
| Oenothera coquimbensis Gay | | a | |
| Oenothera coronopifolia Torr. & A. Gray | | a | |
| Oenothera cruciata Nutt. ex G. Don | Oenothera parviflora L. | | |
| Oenothera cruciformis Kellogg | Chylismia claviformis (Torr. & Frem.) A. Heller subsp. cruciformis (Kellogg) W. L. Wagner & Hoch | | |
| Oenothera curtiflora W. L. Wagner & Hoch | | a | |
| Oenothera curtissii Small | | a | |
| Oenothera curvifolia H. P. Fisch. | Oenothera scabra K. Krause | | |
| Oenothera deltoides Torr. & Frem. | | a | |
| Oenothera deltoides Torr. & Frem. subsp. ambigua (Munz) W. M. Klein | | a | i |
| Oenothera deltoides Torr. & Frem. subsp. cognata (Jeps.) W. M. Klein | | a | i |
| Oenothera deltoides Torr. & Frem. subsp. deltoides | | a | i |
| Oenothera deltoides Torr. & Frem. subsp. eurekensis Munz & John C. Roos | Oenothera californica (S. Watson) S. Watson subsp. eurekensis (Munz & John C. Roos) W. M. Klein | | i |
| Oenothera deltoides Torr. & Frem. subsp. howellii (Munz) W. M. Klein | | a | i |
| Oenothera deltoides Torr. & Frem. subsp. piperi (Munz) W. M. Klein | | a | i |
| Oenothera deltoides Torr. & Frem. var. ambigua Munz | Oenothera deltoides Torr. & Frem. subsp. ambigua (Munz) W. M. Klein | | i |
| Oenothera deltoides Torr. & Frem. var. decumbens (Parry) Munz | Oenothera deltoides Torr. & Frem. subsp. ambigua (Munz) W. M. Klein | | i |
| Oenothera deltoides Torr. & Frem. var. howellii Munz | Oenothera deltoides Torr. & Frem. subsp. howellii (Munz) W. M. Klein | | i |
| Oenothera deltoides Torr. & Frem. var. piperi Munz | Oenothera deltoides Torr. & Frem. subsp. piperi (Munz) W. M. Klein | | i |
| Oenothera densiflora Lindl. | Epilobium densiflorum (Lindl.) Hoch & P. H. Raven | | |
| Oenothera drummondii Hook. | | a | |
| Oenothera drummondii Hook. subsp. drummondii | | a | i |
| Oenothera drummondii Hook. subsp. thalassaphila (Brandegee) W. Dietr. & W. L. Wagner | | a | i |
| Oenothera elata Kunth | | a | |
| Oenothera elata Kunth subsp. elata | | a | i |
| Oenothera elata Kunth subsp. hirsutissima (A. Gray ex S. Watson) W. Dietr. | | a | i |
| Oenothera elata Kunth subsp. hookeri (Torr. & A. Gray) W. Dietr. & W. L. Wagner | | a | i |
| Oenothera elegans H. Lev. | Clarkia unguiculata Lindl. | | |
| Oenothera elongata Rusby | | a | |
| Oenothera erythrosepala (Borbas) Borbas | Oenothera glazioviana Micheli | | |
| Oenothera featherstonei Munz & I. M. Johnst. | | a | |
| Oenothera fendleri A. Gray | Oenothera hartwegii Benth. subsp. fendleri (A. Gray) W. L. Wagner & Hoch | | |
| Oenothera filiformis (Small) W. L. Wagner & Hoch | | a | |
| Oenothera flava (A. Nelson) Garrett | | a | |
| Oenothera franciscana Bartlett | Oenothera elata Kunth subsp. hookeri (Torr. & A. Gray) W. Dietr. & W. L. Wagner | | |
| Oenothera fremontii S. Watson | Oenothera macrocarpa Nutt. subsp. fremontii (S. Watson) W. L. Wagner | | |
| Oenothera fruticosa L. | | a | |
| Oenothera fruticosa L. subsp. fruticosa | | a | i |
| Oenothera fruticosa L. subsp. glauca (Michx.) Straley | | a | i |
| Oenothera gaura W. L. Wagner & Hoch | | a | |
| Oenothera gigas de Vries | Oenothera glazioviana Micheli | | |
| Oenothera glauca Michx. | Oenothera fruticosa L. subsp. glauca (Michx.) Straley | | |
| Oenothera glaucifolia W. L. Wagner & Hoch | | a | |
| Oenothera glazioviana Micheli | | a | |
| Oenothera gracilis Schrad. ex Fisch. & C. A. Mey. | Oenothera perennis L. | | |
| Oenothera grandiflora L'Her. | | a | |
| Oenothera grandis (Britton) Smyth | | a | |
| Oenothera greggii A. Gray var. pubescens A. Gray | Oenothera hartwegii Benth. subsp. pubescens (A. Gray) W. L. Wagner & Hoch | | i |
| Oenothera guadalupensis S. Watson | Camissoniopsis guadalupensis (S. Watson) W. L. Wagner & Hoch subsp. guadalupensis | | |
| Oenothera guadalupensis S. Watson subsp. clementina P. H. Raven | Camissoniopsis guadalupensis (S. Watson) W. L. Wagner & Hoch subsp. clementina (P. H. Raven) W. L. Wagner & Hoch | | i |
| Oenothera hartwegii Benth. | | a | |
| Oenothera hartwegii Benth. subsp. fendleri (A. Gray) W. L. Wagner & Hoch | | a | i |
| Oenothera hartwegii Benth. subsp. filifolia (Eastw.) W. L. Wagner & Hoch | | a | i |
| Oenothera hartwegii Benth. subsp. hartwegii | | a | i |
| Oenothera hartwegii Benth. subsp. maccartii (Shinners) W. L. Wagner & Hoch | | a | i |
| Oenothera hartwegii Benth. subsp. pubescens (A. Gray) W. L. Wagner & Hoch | | a | i |
| Oenothera heterophylla Spach | | a | |
| Oenothera heterophylla Spach subsp. heterophylla | | a | i |
| Oenothera heterophylla Spach subsp. orientalis W. Dietr. et al. | | a | i |
| Oenothera hexandra (Ortega) W. L. Wagner & Hoch | | a | |
| Oenothera hexandra (Ortega) W. L. Wagner & Hoch subsp. gracilis (Wooton & Standl.) W. L. Wagner & Hoch | | a | i |
| Oenothera hexandra (Ortega) W. L. Wagner & Hoch subsp. hexandra | | a | i |
| Oenothera hirtella Greene | Camissoniopsis hirtella (Greene) W. L. Wagner & Hoch | | |
| Oenothera hoelscheri Renner ex Rostanski, nom. inval. | | a | |
| Oenothera hookeri Torr. & A. Gray | Oenothera elata Kunth subsp. hookeri (Torr. & A. Gray) W. Dietr. & W. L. Wagner | | |
| Oenothera hookeri Torr. & A. Gray subsp. hewettii Cockerell | Oenothera elata Kunth subsp. hirsutissima (A. Gray ex S. Watson) W. Dietr. | | i |
| Oenothera hookeri Torr. & A. Gray subsp. hirsutissima (A. Gray ex S. Watson) Munz | Oenothera elata Kunth subsp. hirsutissima (A. Gray ex S. Watson) W. Dietr. | | i |
| Oenothera hookeri Torr. & A. Gray subsp. montereyensis Munz | Oenothera elata Kunth subsp. hookeri (Torr. & A. Gray) W. Dietr. & W. L. Wagner | | i |
| Oenothera hookeri Torr. & A. Gray subsp. venusta (Bartlett) Munz | Oenothera elata Kunth subsp. hirsutissima (A. Gray ex S. Watson) W. Dietr. | | i |
| Oenothera hookeri Torr. & A. Gray subsp. wolfii Munz | Oenothera wolfii (Munz) P. H. Raven et al. | | i |
| Oenothera howardii (A. Nelson) W. L. Wagner | | a | |
| Oenothera humifusa Nutt. | | a | |
| Oenothera indecora Cambess. | | a | |
| Oenothera indecora Cambess. subsp. bonariensis W. Dietr. | Oenothera indecora Cambess. | | i |
| Oenothera jamesii Torr. & A. Gray | | a | |
| Oenothera johnsonii Parry | Oenothera primiveris A. Gray | | |
| Oenothera laciniata Hill | | a | |
| Oenothera laciniata Hill subsp. floridana | Oenothera laciniata Hill | | i |
| Oenothera laciniata Hill subsp. laciniata | Oenothera laciniata Hill | | i |
| Oenothera laciniata Hill subsp. pubescens (Willd. ex Spreng.) Munz | Oenothera pubescens Willd. ex Spreng. | | i |
| Oenothera laciniata Hill subsp. texensis | Oenothera laciniata Hill | | i |
| Oenothera laciniata Hill var. limensis Munz & I. M. Johnst. | Oenothera arequipensis Munz & I. M. Johnst. | | i |
| Oenothera lamarckiana auct. | Oenothera glazioviana Micheli | | |
| Oenothera lamarckiana Ser. | Oenothera grandiflora L'Her. | | |
| Oenothera lavandulifolia Torr. & A. Gray | | a | |
| Oenothera lindheimeri (Engelm. & A. Gray) W. L. Wagner & Hoch | | a | |
| Oenothera lindleyi Douglas | Clarkia amoena (Lehm.) A. Nelson & J. F. Macbr. subsp. lindleyi (Douglas) F. H. Lewis & M. R. Lewis | | |
| Oenothera linifolia Nutt. | | a | |
| Oenothera lipsiensis Rostanski & Gutte | Oenothera parviflora L. | | |
| Oenothera littoralis Schltdl. | Oenothera drummondii Hook. subsp. drummondii | | |
| Oenothera longissima Rydb. | | a | |
| Oenothera longituba W. Dietr. | | a | |
| Oenothera macrocarpa Nutt. | | a | |
| Oenothera macrocarpa Nutt. subsp. fremontii (S. Watson) W. L. Wagner | | a | i |
| Oenothera macrocarpa Nutt. subsp. incana (A. Gray) W. L. Wagner | | a | i |
| Oenothera macrocarpa Nutt. subsp. macrocarpa | | a | i |
| Oenothera macrocarpa Nutt. subsp. mexicana W. L. Wagner | | a | i |
| Oenothera macrocarpa Nutt. subsp. oklahomensis (Norton) W. L. Wagner | | a | i |
| Oenothera mendocinensis Gillies ex Hook. & Arn. | | a | |
| Oenothera mexicana Spach | | a | |
| Oenothera missouriensis Sims | Oenothera macrocarpa Nutt. | | |
| Oenothera missouriensis Sims var. incana A. Gray | Oenothera macrocarpa Nutt. subsp. incana (A. Gray) W. L. Wagner | | i |
| Oenothera mollissima L. | | a | |
| Oenothera montevidensis W. Dietr. | | a | |
| Oenothera multijuga S. Watson | Chylismia multijuga (S. Watson) Small | | |
| Oenothera muricata L. | Oenothera biennis L. | | |
| Oenothera nana Griseb. | | a | |
| Oenothera nuda Renner ex Rostanski, nom. inval. | | a | |
| Oenothera nutans G. F. Atk. & Bartlett | | a | |
| Oenothera oakesiana (A. Gray) J. W. Robbins ex S. Watson | | a | |
| Oenothera odorata Jacq. | | a | |
| Oenothera ovata Nutt. ex Torr. & A. Gray | Taraxia ovata (Nutt. ex Torr. & A. Gray) Small | | |
| Oenothera pallida Lindl. | | a | |
| Oenothera pallida Lindl. subsp. pallida | | a | i |
| Oenothera pallida Lindl. subsp. runcinata (Engelm.) Munz & W. M. Klein | | a | i |
| Oenothera pallida Lindl. subsp. trichocalyx (Nutt.) Munz & W. M. Klein | | a | i |
| Oenothera pallida Lindl. var. runcinata (Engelm.) Cronquist | Oenothera pallida Lindl. subsp. runcinata (Engelm.) Munz & W. M. Klein | | i |
| Oenothera parodiana Munz | | a | |
| Oenothera parodiana Munz subsp. brasiliensis W. Dietr. | Oenothera parodiana Munz | | i |
| Oenothera parodiana Munz subsp. parodiana | Oenothera parodiana Munz | | i |
| Oenothera parviflora L. | | a | |
| Oenothera parviflora L. subsp. angustissima (R. R. Gates) Munz | Oenothera parviflora L. | | i |
| Oenothera parvula Nutt. ex Torr. & A. Gray | Camissonia parvula (Nutt. ex Torr. & A. Gray) P. H. Raven | | |
| Oenothera pedunculifolia W. Dietr. | | a | |
| Oenothera perennis L. | | a | |
| Oenothera peruana W. Dietr. | | a | |
| Oenothera picensis Phil. | | a | |
| Oenothera picensis Phil. subsp. bonariensis W. Dietr. | | a | i |
| Oenothera picensis Phil. subsp. cordobensis W. Dietr. | | a | i |
| Oenothera picensis Phil. subsp. picensis | | a | i |
| Oenothera primiveris A. Gray | | a | |
| Oenothera primiveris A. Gray subsp. primiveris | Oenothera primiveris A. Gray | | i |
| Oenothera pseudoelongata W. Dietr. | Oenothera elongata Rusby | | |
| Oenothera pseudolongiflora W. Dietr. | Oenothera parodiana Munz | | |
| Oenothera pubescens Willd. ex Spreng. | | a | |
| Oenothera pumila L. | Oenothera perennis L. | | |
| Oenothera punae Kuntze | | a | |
| Oenothera purpurata Kleb. | Oenothera biennis L. | | |
| Oenothera purpurea Curtis | Clarkia purpurea (Curtis) A. Nelson & J. F. Macbr. subsp. purpurea | | |
| Oenothera quadrivulnera Douglas | Clarkia purpurea (Curtis) A. Nelson & J. F. Macbr. subsp. quadrivulnera (Douglas) F. H. Lewis & M. R. Lewis | | |
| Oenothera ravenii W. Dietr. | | a | |
| Oenothera ravenii W. Dietr. subsp. argentinae W. Dietr. | Oenothera parodiana Munz | | i |
| Oenothera ravenii W. Dietr. subsp. chilensis W. Dietr. | | a | i |
| Oenothera ravenii W. Dietr. subsp. ravenii | | a | i |
| Oenothera recurva W. Dietr. | Oenothera tarijensis W. Dietr. | | |
| Oenothera refracta S. Watson | Eremothera refracta (S. Watson) W. L. Wagner & Hoch | | |
| Oenothera rhombipetala Nutt. ex Torr. & A. Gray | | a | |
| Oenothera rosea L'Her. ex Aiton | | a | |
| Oenothera rubida Rusby | Oenothera sandiana Hassk. | | |
| Oenothera rubricaulis Kleb. | Oenothera biennis L. | | |
| Oenothera sandiana Hassk. | | a | |
| Oenothera santarii W. Dietr. | | a | |
| Oenothera scabra K. Krause | | a | |
| Oenothera scapoidea Torr. & A. Gray | Chylismia scapoidea (Torr. & A. Gray) Nutt. ex Raim. | | |
| Oenothera scapoidea Torr. & A. Gray var. aurantiaca S. Watson | Chylismia claviformis (Torr. & Frem.) A. Heller subsp. aurantiaca (S. Watson) W. L. Wagner & Hoch | | i |
| Oenothera scapoidea Torr. & A. Gray var. tortilis Jeps. | Chylismia walkeri A. Nelson subsp. tortilis (Jeps.) W. L. Wagner & Hoch | | i |
| Oenothera serrulata Nutt. | | a | |
| Oenothera siambonensis W. Dietr. | | a | |
| Oenothera sinuosa W. L. Wagner & Hoch | | a | |
| Oenothera speciosa Nutt. | | a | |
| Oenothera spectabilis hort. ex Spach | Oenothera elata Kunth subsp. elata | | |
| Oenothera striata Link | Oenothera stricta Ledeb. ex Link subsp. stricta | | |
| Oenothera stricta Ledeb. ex Link | | a | |
| Oenothera stricta Ledeb. ex Link subsp. altissima W. Dietr. | | a | i |
| Oenothera stricta Ledeb. ex Link subsp. argentinae W. Dietr. | Oenothera parodiana Munz | | i |
| Oenothera stricta Ledeb. ex Link subsp. stricta | | a | i |
| Oenothera strigosa (Rydb.) Mack. & Bush | Oenothera villosa Thunb. subsp. strigosa (Rydb.) W. Dietr. & P. H. Raven | | |
| Oenothera strigosa (Rydb.) Mack. & Bush subsp. canovirens (E. Steele) Munz | Oenothera villosa Thunb. subsp. villosa | | i |
| Oenothera strigosa (Rydb.) Mack. & Bush subsp. cheradophila (Bartlett) Munz | Oenothera villosa Thunb. subsp. strigosa (Rydb.) W. Dietr. & P. H. Raven | | i |
| Oenothera suaveolens Pers. | Oenothera biennis L. | | |
| Oenothera suffrutescens (Ser.) W. L. Wagner & Hoch | | a | |
| Oenothera syrticola Bartlett, nom. nud. | Oenothera oakesiana (A. Gray) J. W. Robbins ex S. Watson | | |
| Oenothera tafiensis W. Dietr. | | a | |
| Oenothera tafiensis W. Dietr. subsp. parviflora W. Dietr. | | a | i |
| Oenothera tafiensis W. Dietr. subsp. tafiensis W. Dietr. | | a | i |
| Oenothera tarijensis W. Dietr. | | a | |
| Oenothera tetragona Roth | Oenothera fruticosa L. subsp. glauca (Michx.) Straley | | |
| Oenothera tetraptera Cav. | | a | |
| Oenothera thalassaphila Brandegee | Oenothera drummondii Hook. subsp. thalassaphila (Brandegee) W. Dietr. & W. L. Wagner | | |
| Oenothera torreyi S. Watson | Epilobium torreyi (S. Watson) Hoch & P. H. Raven | | |
| Oenothera trichocalyx Nutt. | Oenothera pallida Lindl. subsp. trichocalyx (Nutt.) Munz & W. M. Klein | | |
| Oenothera triloba Nutt. | | a | |
| Oenothera tubicula A. Gray | | a | |
| Oenothera tubicula A. Gray subsp. strigulosa (Towner) W. L. Wagner & Hoch | | a | i |
| Oenothera tubicula A. Gray subsp. tubicula | | a | i |
| Oenothera tubicula A. Gray var. filifolia Eastw. | Oenothera hartwegii Benth. subsp. filifolia (Eastw.) W. L. Wagner & Hoch | | i |
| Oenothera tucumanensis W. Dietr. | Oenothera siambonensis W. Dietr. | | |
| Oenothera versicolor Lehm. | | a | |
| Oenothera villaricae W. Dietr. | | a | |
| Oenothera villosa Thunb. | | a | |
| Oenothera villosa Thunb. subsp. strigosa (Rydb.) W. Dietr. & P. H. Raven | | a | i |
| Oenothera villosa Thunb. subsp. villosa | | a | i |
| Oenothera viminea Douglas | Clarkia purpurea (Curtis) A. Nelson & J. F. Macbr. subsp. viminea (Douglas) F. H. Lewis & M. R. Lewis | | |
| Oenothera wigginsii W. M. Klein | | a | |
| Oenothera wolfii (Munz) P. H. Raven et al. | | a | |
| Oenothera xenogaura W. L. Wagner & Hoch | | a | |